Cooling heat-generating electronics

1. A server rack sub-assembly, comprising:

at least one motherboard having a perimeter;

a plurality of heat-generating electronic devices mounted on the motherboard in an area of the motherboard that is substantially thermally decoupled from the motherboard perimeter;

an airflow pathway thermally separated from the area of the motherboard that is substantially thermally decoupled from the motherboard perimeter, that is defined along opposed sides of the perimeter of the motherboard from a first edge of the motherboard to a second edge of the motherboard;

one or more brackets comprising heat transfer surfaces and attached to the motherboard within the airflow pathways, the one or more brackets adapted to couple the motherboard to a server rack assembly, the one or more brackets positioned in the airflow pathway to receive a cooling airflow that is circulated within the server rack sub-assembly over the one or more brackets without circulating over the area of the motherboard that is substantially thermally decoupled from the motherboard perimeter; and

a heat transfer device thermally arranged to conductively transfer heat from the one or more electronic devices to the brackets, at least a portion of the heat transfer device including the one or more brackets.

2. The server rack sub-assembly of claim 1 , further comprising a heat sink mounted on the motherboard in the area of the motherboard that is substantially thermally decoupled from the motherboard perimeter, the heat sink thermally coupled to the area of the motherboard and the heat transfer device.

3. The server rack sub-assembly of claim 2 , wherein the heat sink comprises a thermal interface between at least a portion of the plurality of heat-generating electronic devices and a planar portion of the heat sink, the thermal interface adapted to increase contact between the portion of the plurality of heat-generating electronic devices and the heat sink as a temperature of the heat sink increases.

4. The server rack sub-assembly of claim 3 , wherein the thermal interface comprises a phase-change material enclosed against the planar portion of the heat sink by a film, the phase-change material adapted to change from a substantially solid material to a semi-solid or liquid material as the temperature of the heat sink increases.

5. The server rack sub-assembly of claim 4 , wherein the changed phase-change material substantially fills an air gap between the portion of the plurality of heat-generating electronic devices and the heat sink.

6. The server rack sub-assembly of claim 4 , wherein the changed phase-change material substantially fills an air gap between the motherboard and the heat sink.

7. The server rack sub-assembly of claim 1 , wherein the heat transfer device comprises a heat pipe enclosing a working material.

8. The server rack sub-assembly of claim 7 , wherein the heat pipe further comprises an evaporator and at least one condenser, the evaporator thermally coupled to the area of the motherboard thermally decoupled from the perimeter, the condenser thermally coupled to one or more of the brackets.

9. The server rack sub-assembly of claim 7 , wherein the working material is adapted to receive the heat generated by the electronic devices and transfer the heat to the one or more brackets.

10. The server rack sub-assembly of claim 1 , wherein the one or more brackets are adapted to couple at least three motherboards to the server rack assembly.

11. A method for cooling electronic equipment, comprising: providing at least one server rack sub-assembly, comprising:

at least one motherboard;

one or more brackets coupled to the motherboard within airflow pathways that extend along opposed sides of a perimeter of the motherboard between a first edge of the motherboard and a second edge of the motherboard, the one or more brackets adapted to couple the motherboard to a server rack assembly; and

a plurality of heat-generating computing devices mounted on the motherboard in an area that is substantially thermally decoupled from the airflow pathways;

circulating an airflow through the airflow pathways and over the one or more brackets without circulating the airflow over the area that is substantially thermally decoupled from the airflow pathways;

conductively transferring heat generated by the plurality of computing devices mounted on the substantially thermally decoupled area to the one or more brackets; and

convectively transferring the generated heat from the one or more brackets to the cooling airflow.

12. The method of claim 11 , further comprising:

conductively transferring heat generated by the plurality of computing devices mounted on the substantially thermally decoupled area to a heat sink mounted on the motherboard in the area thermally decoupled from the perimeter; and

conductively transferring the heat from the heat sink to the brackets.

13. The method of claim 12 , further comprising:

conductively transferring heat generated by the plurality of computing devices mounted on the substantially thermally decoupled area to the heat sink through a thermal interface between the heat sink and the motherboard, the thermal interface comprising a phase-change material.

14. The method of claim 11 , wherein conductively transferring heat generated by the plurality of computing devices mounted on the substantially thermally decoupled area to the one or more brackets comprises conductively transferring heat generated by the plurality of computing devices mounted on the substantially thermally decoupled area to the one or more brackets with a heat pipe thermally coupled to the motherboard and the one or more brackets, the heat pipe comprising a working material enclosed in an evaporator in fluid communication with a condenser.

15. The method of claim 14 , further comprising:

transferring the generated heat from the plurality of computing devices mounted on the substantially thermally decoupled area to the working material within the evaporator; and

transferring the generated heat from the working material to the one or more brackets.

16. A system comprising:

a server rack assembly;

a server rack sub-assembly, comprising:

at least one motherboard having a perimeter;

an airflow pathway defined along opposed sides of the perimeter of the motherboard from a first edge of the motherboard to a second edge of the motherboard;

a plurality of heat-generating electronic devices mounted on the motherboard in an area of the motherboard that is substantially thermally decoupled from the airflow pathway;

one or more brackets coupling the server rack sub-assembly to the server rack assembly, the one or more brackets comprising heat transfer surfaces and attached to the motherboard within the airflow pathway, the one or more brackets positioned in the airflow pathway to receive a cooling airflow that is circulated within the server rack sub-assembly over the one or more brackets without circulating over the area of the motherboard that is substantially thermally decoupled from the airflow pathway; and

a heat transfer device coupled to the area of the motherboard that is substantially thermally decoupled from the motherboard perimeter, the heat transfer device arranged to conductively transfer heat from the one or more electronic devices to the one or more brackets.

17. The system of claim 16 , further comprising a heat sink thermally coupled between the area of the motherboard that is substantially thermally decoupled from the motherboard perimeter and the heat transfer device.

18. The system of claim 16 , further comprising one or more fans positioned to circulate a cooling airflow across the heat transfer surfaces to convectively remove heat from the heat transfer surfaces.

19. The system of claim 16 , wherein the heat transfer device is a heat pipe.